How global warming will affect our local waters

Study finds ecosystems will have to adapt

Published 10:00 pm, Tuesday, July 24, 2007

Stretches of tidal flats -- home to spindly-legged shoreline birds and clams, snails and crabs -- vanish in some spots, appear in others.

Freshwater marshes turn salty, poisoning plants sensitive to sodium.

As the planet warms and sea levels rise, Washington can expect to see changes such as these along its miles of shoreline, according to a report by the National Wildlife Federation released Tuesday. The report provides the most comprehensive predictions to date about what could happen to these marine ecosystems, tallying how much ocean beach would be lost, for example, while salty marshes expand.

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The news isn't all bad -- but it's mostly not good.

"The problem is the squeeze," said Megan Dethier, a marine biology professor at the University of Washington's Friday Harbor Labs. As water levels rise, creatures and plants are forced inland, where they run smack into people and their roads and houses and businesses.

"We're on the land," Dethier said, "and we're not likely to give it up."

The sea level research comes as efforts are ramping up for a billion-dollar-plus, state-led restoration of Puget Sound, an area that has been, over more than a century, transformed with docks and piers and walls of boulders to slow erosion.

"We don't have a whole lot of healthy habitat left to lose," said Patty Glick, a lead author of the National Wildlife Federation report.

Despite coming from an environmental group, some scientists wondered if the study painted a rosier picture than what the future might actually hold.

It didn't examine the habitat effects of warmer air and water temperatures, saltier water as stream and river levels drop because of shrinking mountain snowpacks, and increasingly acidic marine water as the oceans absorb more carbon dioxide.

Combine that with higher sea levels and "you're just adding chaos," Dethier said.

The report did predict:

Seattle should fare OK overall because most areas are developed and at higher elevation, though more than 700 acres of undeveloped, dry land could become marshy or turned into tidal flats. About half of the beaches along river mouths could be lost by the end of the century as the sea level rises more than two feet.

In Tacoma, dikes would protect the land near the Puyallup River, but about two-thirds of beach areas could be lost because of erosion and flooding.

The Dungeness Spit, a beloved vacation and tourist spot on the Olympic Peninsula, could be whittled down to nearly nothing as more than half of the ocean and river-mouth beaches in the area are swallowed up.

The study didn't make specific predictions about how shellfish, seabirds, salmon and orcas would fare -- but concluded that the loss of habitat likely wouldn't help populations.

Particularly at risk are herring and smelt that spawn on sandy beaches -- little fish that feed birds and bigger fish such as salmon. Also at risk are mussels and clams that can't relocate and must rely on water-borne larvae to spread to new areas as habitats change.

And while many marine species are built to be flexible in new conditions, man-made global warming could stretch them to the breaking point.

"It's definitely unprecedented evolutionarily," Dethier said. "There have been plenty of changes, but they have been very slow. This, presumably, is going to be very fast."

One of the hottest areas of debate in the climate change arena is exactly how fast and far sea levels are likely to rise as oceans warm and expand and polar ice caps melt. By the end of the century, the global average rise could be less than 5 inches at the low end, almost 80 inches at the high end, according to the United Nations Intergovernmental Panel on Climate Change and research published in scientific journals.

The differences depend in large part on the rate of melting for the ice fields in Greenland and Antarctica. The report focused on numbers midway -- 27.3 and 59.1 inches by 2100.

The computer model used to predict the changes also took into account the rise and fall of the land due to movement in geologic faults.

The report is expected to be a useful tool for governments working on shoreline issues. Non-profit groups, scientists and government agencies involved with recovery plans should consider the coming changes when deciding which land to protect or restore, experts said.

It also serves as another reminder that while getting ready for the now-unpreventable changes caused by global warming, quick action is needed to cut greenhouse gas emissions to stave off the most dire damage.

"We're actually talking about preparing for the best-case scenario and fighting like hell to prevent the worst case," said Glick, of the National Wildlife Federation.